Magnets, stabilization

Dry dense medium (pneumatic fluidized-bed) separation has been used, but has not received wide attention by the industry. An area of promise for future development is the use of magnetically stabilized dense medium beds by using ferro or magnetic fluids (2,10). Laboratory and pilot-scale units such as Magstream are available. In this unit, material is fed into a rotating column of water-based magnetic fluid. Particles experience centtifugal forces and... 

New applications and novel reactor configurations or operational modes for three-phase systems are continually being reported. These include the operation of a three-phase fluidized bed in a circulatory mode (Liang et al., 1995), similar to the commonly applied gas-solid circulating fluidized bed the application of a three-phase fluidized bed electrode that can be used as a fuel cell (Tanaka et al., 1990) magnetically stabilized three-phase fluidized beds centrifugal three-phase reactors and airlift reactors. 

Novel Bioparticle Research. Two major thrusts have been seen in recent particle research—the area of density manipulation so that particle density suits the desired fluidization mode, and the development of magnetic particles for use in magnetically stabilized fluidization. Intraparticle mass transfer is also of interest. Table 18 lists several novel particles developed in recent years to address these and other concerns. 

Bramble, J. L., Graves, D. J., and Brodelius, P., Plant Cell Culture Using a Novel Bioreactor The Magnetically Stabilized Fluidized Bed, Biotechnol. Prog.,... 

Siegell, J. H., Liquid-Fluidized Magnetically Stabilized Beds, Powder Tech., 52 139 (1987)... 

Terranova, B. E., and Bums, M. A., Continuous Cell Suspension Processing Using Magnetically Stabilized Fluidized BedsBiotechnol. Bioeng., 37 110... 

Enclosure The main cabinet is divided into two compartments one for the magnet, and one for the electronics. The magnet compartment is maintained at a temperature of 24 + 1 °C for ultimate permanent magnet stability. The electronics compartment is on a separate air conditioner and is less rigorously temperature controlled. Fignre 10.11 shows several pictures of a Qualion Process NMR spectrometer in a NEMA enclosure configured for implementation on-line. 

Bahar, T. and Gelebi, S.S., Performance of immobilized glucoamylase in a magnetically stabilized fluidized bed reactor (MSFBR), Enzyme Microbial Tech., 26 (2000) 28-33. 

S. Chandrasekhar, Hydrodynamic Hydro-magnetic Stability , Clarendon Press, London... 

Fig. 3. Data for sample 2. (a) H-dependence of dV/dl at specified values of I, (b) /-dependence of dV/dl at specified values of H. (c) Magnetization stability diagram extracted from I scans such as shown in (b). Upward (downward) triangles P AP(AP P) switching. A H = —0.5 kOe section shown with dashed fine, (d) MR curves at / = 8 mA, at the specified in-plane angles between H and the nominal easy axis of the nanopillar. AP, P denote the stability region of the respective configurations, P/AP is a bistable region. In (a),(b),(d), thick curves scan from left to right, thin curves scan in opposite direction, curves are offset for clarity.

Graham LJ, Jovanovic G. Dechlorination of p-chlorophenol on a Pd/Fe catalyst in a magnetically stabilized fluidized bed Implications for sludge and liquid remediation. Chem Eng Sci 1999 54 3085-3093. 

To control features of the flow itself (examples include drag reduction by addition of polymer or microbubbles, magnetic stabilization of fluidized beds, foam flow in porous media for mobility control, antimisting or cavitation suppression via polymer additives) and, finally,... 

Stable expanded-bed operations promise the ability to handle whole broths efficiently, all the while maintaining plug-flow characteristics. Magnetically stabilized fluidized beds have been shown to work effectively for bioproduct separations, but are not yet used commercially. A commercially available process uses well-designed beads of appropriate densities and sizes to enable bed fluidization and stable operation without appreciable recirculation. 

Fe/Pt alloys are an important class of materials in permanent magnetic applications because of their large uniaxial magnetocrystalline anisotropy [Xu 7 x 10 J/m j [170] and good chemical stability. As the magnetic stability of individual particles scales with the anisotropy constant, K, and the particle volume, V, small Fe/Pt... 

In an isolation step, where yield and concentration are more important than purity, the adsorption mechanism can be considered an on/off process, and several alternative contacting schemes can be used. Ligands have been bound to magnetized particles (137, 138) for continuous countercurrent adsorption in magnetically stabilized fluidized beds. Ligands attached to liquid perfluorocarbons (143), to dextran and related polymers (144), or incorporated into liposomes (145), or reversed micelles (146) may be used for biospecific liquid-liquid extraction or "affinity partitioning". Ligands have also been attached to surfactants and biopolymers for selective precipitation of dilute protein species (147, 148). 

Burns, M. A. Graves, D. J. "Continuous Affinity Chromatography Using a Magnetically Stabilized Fludized Bed" Biotechnology Progress. 1985, 1, pp 95-103. 

Lochmuller, C. H. Wigman, L. S. "Affinity Separations in Magnetically Stabilized Fluidized Beds Synthesis and Performance of Packing Materials" Sep. Sci. Tech. 1987, 22, pp 2111-2125. 

A mathematical analysis of a crossflow magnetically stabilized fluidized bed chromatograph has been presented (14). The geometry of this system is similar to the rotating annular chromatograph and therefore the modeling approach is quite similar to that reported here. A parametric sensitivity study was conducted and the results indicated that the extent of band broadening was most sensitive to two factors. These factors were the external resistance to mass transfer and the width of the feed band. 

The magnetic particles have a high magnetic stability, which is a necessary condition to obtain the desired shape and size relevant to the requirements of the experiment. The mechanical robustness of the particles was preserved throughout the process. 

Mizukami M, Abe T, Nishihara T (1997) Magnetic stability and noise characteristics of high He CoSm/Cr thin films. IEEE Trans Magn 33 2977-2979... 

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